Numerical prediction for columnar to equiaxed transition in solidified Ti-Al intermetallic alloy ingots by stochastic model

A stochastic model of macro- and microtype for predicting the columnar-equiaxed transition (CET) during solidification processes of Ti-Al intermetallic alloy ingots is developed in the present paper, The macroscopic part is based on a finite difference method (FDM) for modelling of heat transfer. The microscopic part consists of a cellular automaton method (CA) for modelling of nucleation and growth. The formation of a shrinkage cavity at the top of ingot is taken into account. The effects of casting variables on CET are presented and discussed. A quantitative relation between CET position and casting variables is obtained. The columnar zone is found to expand with decreasing alloy composition, mould preheated temperature and convection, and increasing thermal conductivity of mould, superheat and heat transfer coefficient at mould/metal interface. And the highly influential variables are superheat, heat transfer coefficient and convection.